Wheel dollies are known in the art for lifting and moving heavy vehicular wheels. The wheels lifted by a dolly may be separate, or in pairs, and may be fixed to a vehicle. When all the wheels of a vehicle are lifted, if the dollies have their own caster wheels, the entire vehicle may be moved about a workshop to accommodate space requirements.
Commonly, dollies may involve pinching two arms horizontally together toward the perimeter of a wheel. The two arms provide a net upward force vector (and two inward vectors that cancel each other out), the upward force vector lifting the wheel. Alternatively a lifting structure may involve raising two parallel arms vertically upward, the arms carrying the wheel.
Yet, deficiencies remain in the prior art. One shortcoming found in prior art dollies is that they may be structured to require too much surrounding space for safe or efficient operation. For example, when a hydraulic system is used to power the lifting, the user must insert a long handle into the hydraulic unit and pump up the jack to the required extent. Thus, additional space must be found around the dolly for the user to stand and properly activate the hydraulic system. Likewise, when a threaded rod must be rotated, a handle is typically provided attached to the rod, and the user must wind the handle to lift the wheel to the extent required. Again, this requires additional space around the dolly in which the user must position himself to operate the device. In the same way, where a ratchet and pawl system is provided, the user must position himself beside the dolly and pump the ratchet lever to lift the wheel. In many workshop situations, this activity alongside the dolly may be cramped and inconvenient due to space restrictions, and space may be limited (a common feature of many workshops) to the point that the user may find himself obstructed in activating the dolly, or may knock into other sensitive equipment located nearby. To the extent the various levers and handles for activating the dolly protrude from the profile of the dolly, wheeling the dolly about a crowded workshop floor is attended by the added danger of bumping into sensitive equipment.
Another shortcoming in the prior art arises to the extent hydraulic systems are used to power a mechanism to lift the wheel. It is well known that hydraulic systems may be suitable for lifting a load, but they are not suitable for holding a load aloft for any length of time once lifted. This is because hydraulic systems are known to include structure prone to failure, such as O-rings, which may suffer the effects of aging and suddenly give way under load. Thus, where hydraulic systems are used for lifting, they cannot safely be used to hold heavy loads such as vehicles aloft sufficiently long for an artisan to work underneath the load. In short, while they may be used as wheel dollies to merely manipulate a wheel, they cannot safely be used alone as automobile support structure for any length of time. Typically, where hydraulic systems are used to achieve a lifting process in these circumstances, mechanical systems must be additionally introduced to securely support the load and provide safety for an artisan working underneath the vehicle—until such time as the hydraulic system may be used to lower the load once again. This method of operation has the further disadvantage that the additional mechanical system takes up even more room under the vehicle or load, thus denying a clear access to the artisan.
The prior art also lacks adequate simple and rapidly activatable structure to stabilize a dolly in relation to the floor and prevent it from accidentally moving laterally on its casters. Such prevention is especially desirable in the event that dollies are to serve the dual function of wheel handling system and automobile jack. It will be appreciated that an automobile jack that is not laterally stable would be particularly hazardous in use.
Another problem common in prior art dollies is that they do not possess sufficient degrees of freedom for moving a wheel, in that they cannot be controlled easily to position a wheel or an associated vehicular load within a large range of specific locations, both linear and rotational, when the dolly is in a stationary position. For example, some dollies are configured to lift a wheel by moving two parallel arms horizontally toward each other to pinch the wheel from opposite sides below its center point, providing a net upward force vector. However, while this pincer action feature is useful for easily positioning a dolly around the base of a wheel, such a dolly does not have much upward travel—being limited to the height of the arms above the floor. As a result, there may not be enough vertical room under a vehicle lifted in this way to permit an artisan to crawl underneath.
Other dollies have structure that moves directly upward, rather than horizontally, to lift a wheel. However, such dollies may be difficult to position around the base of a wheel because their lifting arms are commonly fixed a set distance apart, or are difficult to adjust. Thus, in dollies with arms horizontally fixed, where the arms are wider apart than necessary to engage a wheel, the arms must be lifted a certain amount before they engage the wheel. The amount thus lifted is lost vertical travel that cannot be imparted to lifting the wheel. Lost vertical travel may adversely affect the ability of the dolly to accomplish an intended task. On the other hand, the fixed arms of such a dolly may be too narrow to engage a large wheel, and in this case the dolly may be unusable.
Thus there is a need for a wheel dolly that may be used as an automobile jack such that it is safe for an artisan to work under loads lifted by the dolly for any length of time without the addition of further mechanical structure. There is a need for a wheel dolly that has increased degrees of freedom to assist in the accurate placement of a wheel or load over a wide range of specific positions. There is a need for a wheel dolly that may be rapidly and easily adjusted, and that does not include levers or handles protruding from the dolly profile that may constitute a hazard while the dolly is being moved, or in operation. The present invention addresses these and other needs.